Such concealing patterns were not of great interest before the First World War, although uniforms were often of a color--khaki, horizon blue, field grey, slate green--which blended into the background. Patterns designed to disrupt the outlines of objects, and hiding objects under a fabric having such a pattern, came into general use in the First World War. This use was greatly expanded subsequently. Disruptive patterns were used for apparel in the Second World War. These patterns do not resemble anything in particular, at near and medium distance they are believed to "break up" the image of the object in the human eye, and in the far distance, above about 600 meters [660 yards], they have a generally drab dirty grey, green or brown appearance, which blends into the background.
Hunters' [as opposed to military] camouflage, is more directed to blending into the background, as exemplified by the dark greenish background coloration of the "hunting" tartans of the Scottish Highland Clans (as opposed to the more flamboyant and highly visible "dress" tartans), or drab colored clothing, which does not stand out at a distance. This distinction is attributed to the believed colorblindness of animals, especially game animals, as opposed to the color vision of humans. Nevertheless many hunters wear apparel having disruptive patterns of the military type as specific hunting camouflage is uncommon. A recent development is color schemes resembling treebark for hunting apparel, while this conceals in the far distance and against suitable backgrounds, it does not conceal against unsuitable backgrounds such as greenwood [spring & summer] foliage.
Development of a suitable pattern for concealment in a hunting environment, which is nearly always leafy, requires study of that environment. Due to human activity, there is little primary, temperate or tropical, climax forest with a high leaf canopy, nearly all leafy environment is secondary growth forest resulting from destruction of the primary forest by human related activities. The most typical feature of secondary growth forest is dense undergrowth composed of smaller species of trees, bushes, shrubs, and saplings of larger species of trees, as the forest attempts to reassert itself. This undergrowth is generally very leafy ranging from 1 to 3 meters [3 to 10 feet] in height, and comprises several species of leafy plants, typically forming numerous thickets. In some areas the entire forest is composed of this sort of growth, for instance after a forest fire or logging.